Kate was the daughter of film producer Lloyd Kingsley-Sayle.
When Kate was six years old, she was kidnapped by Cybermen, had a listening device implanted in her skull, and returned home with no memory of these events.
A year later, her father was making a film about the 1970s Cybermen invasion of Earth. The Second Doctor acted as his scientific adviser and became friends with Kate. Whenever the Doctor changed the script of the film, the Cybermen took note of the change through Kate's implant. After the Doctor had foiled the Cyber invasion, Kate had the implant surgically removed. She also had her tonsils removed. (PROSE: Scientific Adviser)